1. Field of the Invention
The present invention relates to a vibration isolating apparatus in which a plurality of small liquid chambers are disposed between a vibration generating portion and a vibration receiving portion so as to absorb vibrations by means of flow resistance of a liquid moving between the small liquid chambers.
2. Description of the Related Art
A known vibration isolating apparatus for an engine mount, a carburetor mount, a body mount and so forth for use in automobiles is provided with a liquid chamber a part of which is formed of a resilient member. This liquid chamber is partitioned into a plurality of small liquid chambers by partition walls, and the small liquid chambers communicate with each other through restraining passages. For this reason, vibrations are absorbed by resistance occurring when the liquid in one small liquid chamber passes through the restraining passage and moves to another small liquid chamber at the time of occurrence of the vibrations.
With the conventional vibration isolating apparatus, however, since the size of an orifice is uniform, it is possible to absorb vibrations in correspondence with a desired frequency, but it is impossible to cope with vibrations having different frequencies.
For instance, in order to isolate vibrations during engine shaking, if an attempt is made to attenuate the vibrations at frequencies occurring at that time, the orifice becomes clogged during idling when vibrations of higher frequencies are produced, resulting in an increase in the dynamic spring constant. Hence, there is the drawback that the vibration isolating effect declines appreciably during idling.